1. Field of the Invention
The invention relates to switching-mode regulated power supplies.
2. Description of the Prior Art
Regulating devices of the general category into which the invention falls are known per se in the prior art. Such regulators employ a power-switching semiconductor device which is periodically switched on and off (conducting and non-conducting states) by a variable duration control or gating signal. The pulse-width modulation thus achieved is a function of a nominal (or reference) to actual comparison performed during each period (time of each horizontal line in the television receiver case) and thus is line synchronous.
Switching regulators of the type can be implemented in integrated circuit form and have been so described, for example in the well known "Electronic Design" (periodical) of Jan. 18, 1980, pp 94 to 101, and also of Feb. 1, 1979, pp 102. Those references describe switching type regulators which generate pulse-width modulated control signals using analog techniques to make the nominal/actual regulated voltage comparison. Generally in those devices a sawtooth generator serves as the reference voltage, preferably synchronous with the horizontal line rate.
In German patent specification DE-OS No. 28 43 988 a switching-type regulator which develops a pulse-width modulated signal for a power semiconductor is described, however that device relies on a clock pulse cadence without synchronization to a signal such as the horizontal drive of a television receiver. Such additional synchronization is important in the television receiver art as are certain other requirements, including high speed regulation response (during the individual horizontal line period). The microprocessor of DE-OS 28 43 988 could not provide the required speed of regulation response. Other rapid acting features such as overload and short-circuit protection are absent from the aforementioned prior art. Even if added, for example to DE-OS No. 28 43 988, the speed of response in such a combination would preclude use in the television receiver case.
The manner in which the invention deals with the prior art disadvantages to provide a novel combination (particularly effective in the television receiver case) will be understood as this description proceeds.